The overall aim of this research is to analyze the relationships among physiological stimuli (odors), single unit and ensemble physiological responses, and the neuronal circuitry of the olfactory pathway. The encoding of olfactory information initially takes place at the level of the peripheral receptors and is then processed in the olfactory bulb and higher integration centers. The present proposal is designed to examine the response properties of the olfactory receptors using the 2-deoxyglucose (2DG) method, ensemble recording using voltage-sensitive dyes, and reversible receptor block using ultraviolet irradiation after carefully controlled odor presentation. The properties of the receptors examined using these methods will be correlated with responses observed in cells from the olfactory bulb. The bulbar cells and their associated circuitry will be studied using techniques of precise odor stimulus application, extra- and intracellular recording, horseradish peroxidase staining, 2DG metabolic mapping, and voltage-sensitive dye recording. The salamander has been chosen as a model system for these purposes because of its demonstrated anatomical, physiological, and behavioral advantages. It is anticipated that these studies will not only provide insight into mechanisms by which odors are encoded by the CNS, but also will yield information on local circuit mechanisms in the olfactory bulb that may have applicability to local circuit interactions in other brain regions. The olfactory pathway provides one of the principle sensory inputs to several phylogenetically old brain regions, including the pyriform cortex, olfactory tubercle, and amygdala. As such study of the olfactory pathway may provide a window through which to investigate these areas which relate to critical behaviors including food recognition and mate selection in animals, and abnormal brain states such as epilepsy and schizophrenia in humans. One of the first steps in analyzing how these higher relays function is to investigate the inputs to them. It is investigation of this initial stage of processing of odor information for which this proposal seeks support.